drivers/base/power/sysfs.c

   1 /*
   2  * drivers/base/power/sysfs.c - sysfs entries for device PM
   3  */
   4
   5 #include <linux/device.h>
   6 #include <linux/string.h>
   7 #include "power.h"
   8
   9 int (*platform_enable_wakeup)(struct device *dev, int is_on);
  10
  11
  12 /*
  13  *      wakeup - Report/change current wakeup option for device
  14  *
  15  *      Some devices support "wakeup" events, which are hardware signals
  16  *      used to activate devices from suspended or low power states.  Such
  17  *      devices have one of three values for the sysfs power/wakeup file:
  18  *
  19  *       + "enabled\n" to issue the events;
  20  *       + "disabled\n" not to do so; or
  21  *       + "\n" for temporary or permanent inability to issue wakeup.
  22  *
  23  *      (For example, unconfigured USB devices can't issue wakeups.)
  24  *
  25  *      Familiar examples of devices that can issue wakeup events include
  26  *      keyboards and mice (both PS2 and USB styles), power buttons, modems,
  27  *      "Wake-On-LAN" Ethernet links, GPIO lines, and more.  Some events
  28  *      will wake the entire system from a suspend state; others may just
  29  *      wake up the device (if the system as a whole is already active).
  30  *      Some wakeup events use normal IRQ lines; other use special out
  31  *      of band signaling.
  32  *
  33  *      It is the responsibility of device drivers to enable (or disable)
  34  *      wakeup signaling as part of changing device power states, respecting
  35  *      the policy choices provided through the driver model.
  36  *
  37  *      Devices may not be able to generate wakeup events from all power
  38  *      states.  Also, the events may be ignored in some configurations;
  39  *      for example, they might need help from other devices that aren't
  40  *      active, or which may have wakeup disabled.  Some drivers rely on
  41  *      wakeup events internally (unless they are disabled), keeping
  42  *      their hardware in low power modes whenever they're unused.  This
  43  *      saves runtime power, without requiring system-wide sleep states.
  44  */
  45
  46 static const char enabled[] = "enabled";
  47 static const char disabled[] = "disabled";
  48
  49 static ssize_t
  50 wake_show(struct device * dev, struct device_attribute *attr, char * buf)
  51 {
  52         return sprintf(buf, "%s\n", device_can_wakeup(dev)
  53                 ? (device_may_wakeup(dev) ? enabled : disabled)
  54                 : "");
  55 }
  56
  57 static ssize_t
  58 wake_store(struct device * dev, struct device_attribute *attr,
  59         const char * buf, size_t n)
  60 {
  61         char *cp;
  62         int len = n;
  63
  64         if (!device_can_wakeup(dev))
  65                 return -EINVAL;
  66
  67         cp = memchr(buf, '\n', n);
  68         if (cp)
  69                 len = cp - buf;
  70         if (len == sizeof enabled - 1
  71                         && strncmp(buf, enabled, sizeof enabled - 1) == 0)
  72                 device_set_wakeup_enable(dev, 1);
  73         else if (len == sizeof disabled - 1
  74                         && strncmp(buf, disabled, sizeof disabled - 1) == 0)
  75                 device_set_wakeup_enable(dev, 0);
  76         else
  77                 return -EINVAL;
  78         return n;
  79 }
  80
  81 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
  82
  83
  84 static struct attribute * power_attrs[] = {
  85         &dev_attr_wakeup.attr,
  86         NULL,
  87 };
  88 static struct attribute_group pm_attr_group = {
  89         .name   = "power",
  90         .attrs  = power_attrs,
  91 };
  92
  93 int dpm_sysfs_add(struct device * dev)
  94 {
  95         return sysfs_create_group(&dev->kobj, &pm_attr_group);
  96 }
  97
  98 void dpm_sysfs_remove(struct device * dev)
  99 {
 100         sysfs_remove_group(&dev->kobj, &pm_attr_group);
 101 }